Present telecommunication system technology includes a wide variety of wireless networking systems associated with both voice and data communications. As overview of several of these wireless networking systems is presented by Amitava Dutta-Roy, Communications Networks for Homes, IEEE Spectrum, pg. 26, December 1999. Therein, Dutta-Roy discusses several communication protocols in the 2.4 GHz band, including IEEE 802.11 direct-sequence spread spectrum (DSSS) and frequency-hopping (FHSS) protocols. A disadvantage of these protocols is the high overhead associated with their implementation. A less complex wireless protocol known as Shared Wireless Access Protocol (SWAP) also operates in the 2.4 GHz band. This protocol has been developed by the HomeRF Working Group and is supported by North American communications companies. The SWAP protocol uses frequency-hopping spread spectrum technology to produce a data rate of 1 Mb/sec. Another less complex protocol is named Bluetooth™ after a 10th century Scandinavian king who united several Danish kingdoms. This protocol also operates in the 2.4 GHz band and advantageously offers short-range wireless communication between Bluetooth™ devices without the need for a central network.
The Bluetooth™ protocol provides a 1 Mb/sec data rate with low energy consumption for battery powered devices operating in the 2.4 GHz ISM (industrial, scientific, medical) band. The current Bluetooth™ protocol provides a 10-meter range and a maximum asymmetric data transfer rate of 723 kb/sec. The protocol supports a maximum of three voice channels for synchronous, CVSD-encoded transmission at 64 kb/sec. The Bluetooth™ protocol treats all radios as peer units except for a unique 48-bit address. At the start of any connection, the initiating unit is a temporary master. This temporary assignment, however, may change after initial communications are established. Each master may have active connections of up to seven slaves. Such a connection between a master and one or more slaves forms a “piconet.” Link management allows communication between piconets, thereby forming “scatternets.” Typical Bluetooth™ master devices include cordless phone base stations, local area network (LAN) access points, laptop computers, or bridges to other networks. Bluetooth™ slave devices may include cordless handsets, cell phones, headsets, personal digital assistants, digital cameras, or computer peripherals such as printers, scanners, fax machines and other devices.
The Bluetooth™ protocol uses time-division duplex (TDD) to support bidirectional communication. Frequency hopping permits operation in noisy environments and permits multiple piconets to exist in close proximity. The frequency hopping scheme permits up to 1600 hops per second over 79 1-MHZ channels or the entire 2.4 GHz ISM spectrum. Various error correcting schemes permit data packet protection by ⅓ and ⅔ rate forward error correction. Further, Bluetooth™ uses retransmission of packets for guaranteed reliability. These schemes help correct data errors, but at the expense of throughput.
The Bluetooth™ protocol is specified in detail in Specification of the Bluetooth System, Version 1.0A, Jul. 26, 1999, which is incorporated herein by reference.
The Bluetooth™ standard currently allows only 7 active slaves within a piconet. This is because there is only a 3-bit active member address field, so there are only 8 addresses available. One of these addresses is reserved for broadcast packets, leaving only 7 addresses available for active slaves. In some cordless telephone applications, such as in a small office environment, there may be a need to support 12 or more slave devices, i.e., cordless telephones.
It is therefore desirable to extend the addressing capabilities of wireless communication systems such as Bluetooth™ systems.
The invention provides extended addressing capability in a Bluetooth™ system. According to the invention, one existing address code in an address field of a packet is used to indicate that bits in another field of the packet represent additional address information. Further according to the present invention, the address field can be extended in order to provide a plurality of additional address codes. These extended addressing capabilities also provide backward compatibility to conventional Bluetooth™ devices.